Method and apparatus for indirect bonding of orthodontic appliances to teeth

ABSTRACT

A method of indirect bonding and a physical model that allows for optimal positional alignment of orthodontic appliances on a patient&#39;s teeth is disclosed. The physical model of the patient&#39;s teeth has pods and ridges on the facial surface of the teeth. Adhesive is applied to an orthodontic appliance and the appliance is placed on a tooth of the physical model against the ridge and on top of the pods. The adhesive fills the space in between the appliance and the facial surface of the tooth and adheres to the model, resulting in a dimensionally correct custom base that is properly aligned with the tooth to account for all five positional elements of a tooth. Once all the orthodontic appliances are applied to the model, the appliances can then be removed from the model and bonded to the patient&#39;s teeth in the optimal position using a transfer template.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the field of orthodontics and, moreparticularly, to the fabrication of a physical model that serves as aguide for the proper placement of orthodontic appliances, especiallybrackets, on a patient's teeth when utilizing any of several indirectbonding techniques.

2. Description of Related Art

Orthodontics involves repositioning the teeth to correct a malocclusion.This repositioning can be accomplished using various forms oforthodontic appliances or apparatuses. Fixed orthodontic treatmentgenerally involves the bonding or cementation of bands, brackets, andtubes (collectively “braces”) to the teeth. The brackets and tubes serveas “handles” by which gentle forces can be applied to the teeth.Archwires are placed into the bracket slots to achieve the basicalignment direction and forces. Various combinations of elastomeric,elastic, coil spring, and other devices can be used to provideadditional, specific forces to the teeth. Proper placement of thebrackets on a patient's teeth is one of the most significantdeterminants of effective tooth movement to the desired location.

The most common form of “braces” is brackets that are bonded to thesurface of the teeth. Two techniques for placing brackets on a patient'steeth are direct bonding and indirect bonding. Direct bonding is anintraoral procedure in which orthodontic appliances are oriented byinspection and bonded individually to the tooth surface by the doctor orauxiliary personnel. Indirect bonding is basically a two-step process bywhich brackets are affixed temporarily to the teeth of a physical modelfor that specific patient and then transferred all together to the mouthby means of a molded matrix or transfer tray that captures theirpredetermined orientation and permits them to be bonded simultaneously.

Advantages of indirect bonding compared to direct bonding include moreaccurate bracket placement, improved access, simultaneous bonding of allbrackets, shorter bonding appointment times, and less re-positioning ofthe brackets due to placement errors. Ideal bracket positioning is thegoal that should reduce adjustments to the archwires. All of theseadvantages result in decreased chair time, decreased orthodontist time,less treatment time, and less patient discomfort.

However, orthodontists are still dissatisfied with available direct andindirect bonding because existing techniques do not allow theorthodontist to optimally position orthodontic appliances in threedimensions relative to the tooth surfaces. In particular, thesetechniques do not take into account all five positional elements of apatient's teeth: rotation, height, angulation (or tip), torque, andin-out. Further, these existing techniques of indirect bonding provideminimal guidance as to how the actual position of a bracket compares tothe clinician-defined prescription.

Therefore, a need exists for a physical bonding model and a method ofindirect bonding that assist with optimal positional alignment of thebrackets on the patient's teeth by taking into consideration all fivepositional elements of a patient's teeth. A need also exists for amethod that even more so decreases chair time, decreases orthodontisttime, lessens treatment time and lessens patient discomfort.

SUMMARY OF THE INVENTION

Orthodontic appliances such as orthodontic brackets or tubes typicallyinclude a retentive bonding pad or base, a body with a slot into whichan archwire can be placed, and tie wings or ligating mechanisms to holdthe archwire in place. According to one embodiment of the invention, aphysical model is disclosed that comprises a three dimensional solidrepresentation of one or more maloccluded teeth. The model furthercomprises a plurality of structures disposed on the facial surface ofeach model tooth for use in preferentially positioning an orthodonticappliance in three dimensions relative to the facial surface.

The positioning structures disclosed herein preferably include at leasttwo ridge portions and from one to four pods. Each ridge portionpreferably contacts and serves as a positioning guide for a differentside portion of the bonding pad or base member of an orthodonticappliance, and two or more ridge portions can cooperate topreferentially position the appliance in the x- and y-dimensionsrelative to the facial surface of a model tooth. The pod or podspreferably contact the underside of an orthodontic appliance topreferentially position the base of the appliance in the z-dimensionrelative to the facial surface of a model tooth. The ridge portions andpods are preferably formed as a unitary part of a physical model that ismade from a virtual model on which the preferred ridge and podconfigurations for each tooth are determined. The ridges can, but neednot, intersect, and the height of each pod can vary within practicallimits determined by factors such as the base area of the orthodonticappliance, interference with adjacent model teeth due to inclination andspacing, and the like.

Once the positional relationship of the appliance base to the facialsurface of the model tooth is determined in all three dimensions bymeans of the ridge portions and pod or pods, each appliance can betemporarily cemented to its respective model tooth using a releasableadhesive. Because the releasable adhesive will fill in the spaces aroundthe pods beneath the base of the orthodontic appliance prior to curing,a solid, three dimensional bonding pad is formed beneath the base thatwill cause the appliance to reestablish the same positional alignmentrelative to the actual tooth from which the model was made when theappliance is removed from the model tooth and transferred to the actualtooth using indirect bonding techniques. The orthodontic appliance isthereby optimally positioned in a predetermined, desired positionalrelationship to the facial surface of the actual tooth for theapplication of therapeutic forces during treatment to achieveadjustments in rotation, height, angulation (or tip), torque, andin-out. This process can be accomplished quickly and effectively byusing a transfer tray to lift and move the appliances from as many as 16model teeth at once.

According to another preferred embodiment of the invention, an indirectbonding method is disclosed that begins by obtaining a direct impressionor scanned image of the patient's teeth. The impression is convertedinto a digital image or a virtual model of the original malocclusion.Using any of several software applications, the teeth of the virtualmodel are manipulated to create the ideal corrected occlusion. Virtualbrackets and tubes of various types as may be desired by the orthdontistare applied to the virtual model, and the software is then utilized todetermine the optimum bracket position based on the final correctedocclusion.

According to one particularly preferred embodiment, the software thenestablishes the height and positioning of one vertical ridge and onehorizontal ridge that serve as guides for the anterior-posterior ormesial-distal position (rotation) and the superior-inferior orocclusal/incisal-gingival position of the bracket base (height), orgenerally, the x and y axes. Since the contours of the tooth surface andthe bracket base or pad are not necessarily congruent, the software thengenerates between one and four small, spaced-apart, pods of variousheights, or other similarly effective spacers, for orienting the base ofthe orthodontic appliance relative to the surface of the virtual toothin the “z” dimension. The “z” dimension can be referred to as “complexin and out” positioning of the bracket base, which affects torque,rotation, and actual in and out positioning of the brackets. Theplacement, position, and dimensions of the pods and ridges created bythe computer software are based on the teeth in their corrected positionas shown by the corrected virtual model. For purposes of thisdisclosure, the x, y, and z coordinate system discussed herein ispreferably oriented so that, with regard to any particular tooth, thex-y plane lies in the facial surface of the tooth. The “x” direction istowards the mesial or distal surface of the tooth, the “y” direction istowards the gingival or incisal or occlusal surface of the tooth, andthe “z” direction is away from the facial surface of the tooth.

The virtual corrected model with virtual brackets in place is then“re-wound” to the original malocclusion position. Any interferences withbracket placement in the maloccluded state is determined andaccommodated. Ideal bracket placement may not be possible until furthertooth movement has occurred. Likewise, the placement of aligning ridgesand pods may require modification from the ideal, as discussed below.

Next, a physical model is created, preferably using a stereolithographic process or other similarly effective method, with theappropriate ridges and pods on the surface of each tooth. The pods onthe model control the spacing of the individual bracket bases or padsfrom the tooth and its angular relationship to the face of the tooth,and account for the torque and in-out positional elements (collectively“complex in-out”) of the tooth. The ridges control theanterior-posterior (mesial-distal) and the superior-inferior (occlusalor incisal-gingival) positioning of the brackets and account for theheight, rotation and angulation (or tip) positional elements of thetooth. In sum, the pods and ridges act cooperatively to preciselyposition the brackets in all three dimensions for maximum therapeuticbenefit in moving the teeth to where they will eventually be in theircorrected position.

After the physical model with the pods and ridges is created, adhesivethat releasably mounts the brackets to the model is applied to the baseof the brackets. Each bracket is placed in contact with the ridges onthe tooth of the physical model to align the tooth in regard to height,rotation and angulation. The bracket is fully seated onto the pods. Theadhesive enters the space between the tooth surface and the base of thebracket as it is supported by the pods to fill the void and form adimensionally correct, custom-contoured bonding base.

The adhesive holding the brackets onto the model is then cured. Thecured adhesive is permanently attached to the bracket pad or base butreleasably attached to the physical model. A transfer tray is formed andmolded over the brackets on the model. The transfer tray and model arethen soaked in water to release the brackets from the model. Aftersoaking, the transfer tray while gripping the brackets is removed fromthe model. A bonding agent is then applied to the brackets and thetransfer tray transfers the brackets from the model to the patient'steeth. The transfer tray can transfer a plurality of brackets at once,or it can transfer one bracket at a time if the bracket needs to bereplaced on a single tooth.

As a result of optimally positioning the bracket to take intoconsideration the five positional elements of a tooth, the archwire canbe secured to the brackets with less custom bonding and fitting, andwill apply forces to the teeth to move them more efficiently andeffectively to the desired position. Use of the present inventionreduces the need for adjusting the archwire and replacing orrepositioning brackets, thereby also reducing orthodontist time,treatment time, chair time and patient discomfort.

BRIEF DESCRIPTION OF THE DRAWINGS

The apparatus of the invention is further described and explained inrelation to the following figures of the drawings wherein:

FIG. 1 is a perspective view of a physical bonding model of theinvention with ridges and pods incorporated on a facial surface ofteeth;

FIG. 2 is a detail view of a portion of the physical bonding model ofFIG. 1;

FIG. 3 is a side detail view taken along line 3-3 of FIG. 2;

FIG. 4 is a perspective view of a physical bonding model of theinvention showing brackets in contact with ridges and pods on a facialsurface of teeth;

FIG. 5 is a detail view of a portion of the physical bonding model ofFIG. 4;

FIG. 6 a is an exploded cross-sectional view taken along line 6-6 ofFIG. 5 and illustrates adhesive applied to the underside of a bracketthat will surround pods;

FIG. 6 b is a view as in FIG. 6 a but showing a bracket releasablymounted on a model with adhesive surrounding pods;

FIG. 7 is an enlarged perspective view of a bracket with a mesh base;

FIG. 8 a is an elevation view of a bracket releasably mounted on a toothwith a negative torque and showing pods supporting the bracket in alevel position, partially spaced away from the tooth surface withrespect to a z-axis;

FIG. 8 b is an elevation view of a bracket releasably mounted on a toothwith a positive torque and showing pods supporting the bracket in alevel position, partially spaced away from the tooth surface withrespect to a z-axis;

FIG. 8 c is an elevation view of a bracket releasably mounted on a tooththat is set-back and showing adhesive spacing the bracket away from thetooth surface;

FIG. 9 is a perspective view of a physical bonding model showing amaterial being molded over teeth and brackets to form a transfer tray;

FIG. 10 is a perspective view of a physical bonding model showingbrackets being lifted from a model and held in a transfer tray;

FIG. 11 is a fragmentary view taken along line 11-11 of FIG. 10 showinga portion of the transfer tray with brackets held inside;

FIG. 12 is a detail view taken from FIG. 11 showing an underside of abracket having adhesive thereon and showing indentations in the adhesiveleft by pods; and

FIG. 13. is a front view of brackets bonded to a patient's teeth with atransfer tray removed.

Like reference numerals are used to describe like parts in all figuresof the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The method of the invention preferably begins with taking an impressionof the patient's maloccluded teeth, which is used to form a plaster orstone tooth impression model. The impression model is then sent to alaboratory, scanned and converted into a digital file to form a virtualmodel. Although the use of an impression is a preferred method forcreating a virtual model, other similarly effective alternative methodssuch as intra-oral scanning of the teeth can also be used. The originalvirtual malocclusion model is then manipulated using specializedcomputer software to reposition the teeth to their final or correctedstate. This final or corrected state is used to create another virtualmodel, the corrected malocclusion model.

From the corrected malocclusion model, the ideal position of a virtualorthodontic appliance on the original malocclusion model can bedetermined. The virtual orthodontic appliance can be placed on a toothof the original malocclusion model in an optimal location to account forall five positional elements of the tooth, which include height,rotation, angulation, torque and in-out, terms well known toorthodontists. This optimal appliance location can be used to applyforces to the tooth through an archwire and the appliances to move themaloccluded tooth to the position of the corresponding tooth in thecorrected malocclusion model quickly and precisely. However, the idealposition of the orthodontic appliance as shown in the virtual model maynot even be touching the facial surface of the tooth. In such cases,proper positioning of the appliance relative to the tooth requires somemeans for spacing the orthodontic appliance away from, or at apredetermined angle relative to, the tooth.

Based on this ideal position of the orthodontic appliance, at least one,and preferably one to four, virtual pods or bosses and at least twovirtual ridge portions are created on the virtual original malocclusionmodel using computer software. Although the ridge portions and pods ofthe invention are explained in more detail below, the ridge portions actas guides to properly position the base of the appliance in the X- andY-dimensions on the facial surface of the tooth, and to indicate wherethe appliance, such as a bracket, should be located relative to thefacial surface of the tooth. The pods then preferably support the baseof the appliance at the desired distance from the facial surface of themodel tooth and in the proper orientation relative to the facialsurface.

It should be noted that not every tooth in a virtual or physicalmalocclusion model will necessarily have ridges portions or pods. Someteeth may have only a partial ridge. A tooth may be so severely malposedthat positioning the orthodontic appliance on the tooth would cause acollision or interference with the next tooth or bracket. In this case,the tooth will have to be moved incrementally and the bracket resetlater. For this purpose, a second physical model with the teeth in thefully corrected positions should be produced. In some situations, atransfer tray can be created for a single tooth.

Once the ridge portions and pods are created on the virtual malocclusionmodel, a positive model embodying the same ridge portions and pods ismanufactured from the virtual malocclusion model. One preferredapparatus suitable for use in fabricating a positive model from thevirtual model is a stereo lithography apparatus (SLA). Simply stated,the SLA utilizes a controlled laser beam to selectively harden athermosetting liquid resin into a physical structure corresponding tothe virtual malocclusion model bearing the pods and ridges on the facialsurface of the teeth. More detailed descriptions regarding SLA and othercomputer-aided fabrication techniques are publicly available, forexample, in U.S. Pat. Nos. 6,699,037 and 6,688,885. Various commerciallyavailable materials can be used to create the positive malocclusionmodel, provided that the adhesive applied to the orthodontic appliancesticks but does not permanently adhere to the model.

It should also be understood that the method used to fabricate aphysical model does not necessarily have to rely on computermanipulation of digital data. The present invention may, for example, beproduced manually without using computer-aided techniques. For instance,the tooth impression model can be duplicated and one of the models canitself be manually manipulated to reposition the teeth into a correctedposition. Based on this corrected position and the placement of theorthodontic appliances on the positive malocclusion model to efficientlyand effectively achieve the corrected position, ridges can be formed onthe malocclusion model to serve as guides for positioning the edge ofthe base of an orthodontic appliance relative to the facial surface of atooth. Similarly, pods can be formed on the positive malocclusion modelusing plaster, for example, to fill in any voids between the facialsurface of the tooth and the base of a correctly positioned orthodonticappliance. Although the present invention can be implemented using thismanual method, the computer-aided techniques are preferred because theyare more accurate and less time consuming.

Referring to FIG. 1, physical model (10) comprises teeth (12) implantedin gingival tissue (14). Facial surfaces (16) of teeth (12) include atleast one pod (18) or boss and, preferably, at least two cooperatingalignment ridge portions (20). FIGS. 2 and 3 show detail views of pods(18) and ridges (20).

Pods (18) are preferably dome-shaped to allow the orthodontic applianceto release more easily from pod (18). Pods (18) may need to be moretapered toward their gingival side so that as the orthodontic applianceis removed, the appliance can flex and slide over pod (18). Thedimensions of individual pods (18) can vary as needed to obtain properspatial alignment of the appliance relative to teeth (12) but preferablydo not exceed about half a millimeter in height and diameter. The poddimensions will typically need to be of a height and geometry thatfacilitates withdrawal of the orthodontic appliance.

The number, position, height and orientation of pods (18) on tooth (12)are preferably determined by the computer software based on thedimensions of the teeth and any interference between them. Althoughthree pods can often stabilize an orthodontic appliance on a modeltooth, the use of four pods per tooth will typically guaranteestability. In other cases, one or two pods may be all that is needed foroptimal spatial positioning of the orthodontic appliance in relation tothe facial surface of a tooth. The pods may, for example, be orienteddiagonally or across from each other. While the use of from one to fourpods is preferred, it should be understood that some model teeth mayrequire no pods and the total number of pods per tooth is not limited tofour.

Alignment ridges (20) preferably include horizontal ridge portion (22)along the x-axis and vertical ridge portion (24) along the y-axis ofmodel (10). “X” ridge portion (22) and “y” ridge portion (24) preferablyintersect to form a right angle or corner (25), although it is notrequired that the cooperating ridge portions intersect or abut eachother, or that they be at right angles to each other, so long as theircombined effect is to properly position an orthodontic appliance in thex-y plane on the facial surface of a model tooth.

“X” ridge portion (22) is preferably placed on the occlusal or incisalsurface of tooth (12) to allow for trimming of the orthodontic applianceon its gingival margin, as the appliance is almost never trimmed on itsocclusal or incisal margins. The “y” ridge portion is preferably placedon either the mesial surface or distal surface depending on the rotationof tooth (12) and access with the orthodontic appliance. “Y” ridgeportion (24) is shown in solid outline on the distal surface and “y”ridge portion (24′) is shown in dashed outline on the mesial surface.One of the vertical margins of the orthodontic appliance may need to betrimmed to clear an adjacent tooth, so “y” ridge portion (24) ispreferably placed on the untrimmed side. However, it should beunderstood that in rare cases, neither the mesial surface nor the distalsurface is accessible for an untrimmed orthodontic appliance. In thesecases, another physical malocclusion model with the alignment ridges andpods can be created from the virtual model depicting the partiallycorrected tooth position after real tooth movement produces sufficientclearance to allow access. The height, length and width of alignmentridges can vary within the scope of the invention and will mostpreferably be of a height and geometry that facilitates the placement ofa corner of an orthodontic appliance against the ridge. For example, the“x” ridge and “y” ridge portions on one tooth may not have the samedimensions based on the extent the bracket is spaced from the facialsurface of the tooth.

Once the physical model (10) bearing the ridge portions and pods asdescribed above is formed, the orthodontic appliances can be placed onthe model teeth (12). As previously mentioned, the orthodonticappliances are preferably brackets or buccal tubes. Referring to FIG. 7,bracket (26) of the invention is a commercially available orthodonticappliance that is bonded to the patient's tooth for the purpose offastening an archwire. Bracket (26) is preferably fabricated from metal,ceramic, or plastic, or a combination of any of the three materials.Bracket (26) shown in FIG. 7 is designed to bond to incisors orbicuspids and includes a body (28) which has a slot (30) to receive thearchwire. The underside of body (28) of bracket (26) is attached to apad (32) and the underside of pad (32) is attached to a mesh base (34).In contrast to the bracket shown in FIG. 7, orthodontic appliances usedwith molars commonly have tubes where the end of the archwire isreceived. These appliances are often referred to as “buccal tubes.”However, it should be understood that the method of the invention can beutilized with brackets that attach to incisors or bicuspids, buccaltubes that attach to the molars, or any other device that can be mountedonto a patient's tooth to receive an archwire or head gear. Throughoutthe disclosure, brackets and buccals tube are used as examples oforthodontic appliances that can be efficiently and effectivelypositioned through use of the present invention.

FIG. 4 illustrates a plurality of brackets (26) mounted on facialsurface (16) of teeth (12) and a bracket (26) about to be placed onfacial surface (16) of model tooth (12). FIG. 5 shows a detailed view ofthe plurality of mounted brackets (26) of FIG. 4. To mount brackets(26), liquid adhesive (36) is applied to mesh base (34), as shown inFIG. 6A. Adhesive (36) is preferably selected from various commerciallyavailable adhesive materials that will attach more securely, forexample, to the mesh bonding pad typically found on the underside of thebase of brackets (26) than to the relatively slicker surface of model(10). Properly positioned and aligned brackets (26) should be releasablefrom model (10) even after the adhesive sets sufficiently to form asolid bonding pad capable of supporting bracket (26) in a preferredpositional and spatial alignment relative to model tooth (12).

Bracket (26) with adhesive (36) is desirably placed on tooth (12) ofmodel (10) with slot (30) oriented relative to facial surface (16) oftooth (12) so that an archwire can be attached to a plurality ofbrackets. Bracket (26) is placed with one corner of pad (32) of bracket(26) contacting corner (25) of ridge (20), and with mesh base (34) ofbracket (26) contacting pods (18). The contact between pods (18) andmesh base (34) is shown in FIG. 6 b, where it is also shown that anysurplus adhesive (36) is removed after positioning the bracket on themodel.

The contact between mesh base (34) and pods (18) allows the adhesive onmesh base (34) around pods (18) to create a thickness of layer based onthe height of the pod. The higher the pod, the thicker the adhesive.This thickness spaced bracket (26) away from tooth (12) along the z-axis(which is labeled in FIGS. 8 a, 8 b and 8 c) and accounts for thecomplex in-out dimension of tooth (12) to optimally position bracket(26) on tooth (12).

Multiple pods (18) associated with a single tooth (12) can have varyingheights, which in turn means that adhesive (36) adhering to bracket (26)placed on tooth (12) can have varying thickness. FIGS. 8 a and 8 b showexamples of this variation. FIG. 8 a illustrates that pod (18) nearocclusal surface or incisal surface (38) is taller than pod (18) neargingival surface (40). Altering the pod heights, thereby altering thebracket postion in the z-dimension, will alter the torque properties forany given bracket placement in the x- and y-dimensions. For example,adhesive (36) is thicker near occlusal surface or incisal surface (38)than it is near gingival surface (40). This thickness near occlusalsurface or incisal surface (38) accounts for the excess negative torqueor the crown of tooth (12) tipping in. Because of the negative torque,bracket (26) has been raised by adhesive (36) at an angle (θ) in thez-axis direction.

In contrast, in FIG. 8 b, pod (18) near gingival surface (40) is tallerthan pod (18) near occlusal surface or incisal surface (38) and,therefore, adhesive (36) is thicker near gingival surface (40) than nearocclusal surface or incisal surface (38). This thickness near gingivalsurface (40) accounts for the excess positive torque or the crown oftooth (12) tipping out. Because of the positive torque, bracket (26) hasbeen raised by adhesive (36) at an angle (θ) in the z-axis direction.

Pods (18) may also be the same height, as shown in FIG. 8 c, if tooth(12) does not have much inclination or rotation, or if tooth (12) isnear its corrected or final position. In this case, bracket (26) hasbeen raised straight up in the z-axis direction so that slot (30) willline up evenly with other slots so that an archwire mounted to brackets(26) is essentially straight. As mentioned previously, pods (18) controlthe complex in-out positional element of a tooth by controlling thespacing of an individual bracket away from the tooth and by controllingthe bracket's angular relationship to facial surface of the tooth (16).

As best illustrated in FIG. 5, one corner of bracket (26) is in contactwith corner (25) of ridge (20). This contact permits the side walls ofpad (32) to align with the inside walls of “x” ridge portion (22) and“y” ridge portion (24) in order to align bracket (26) on tooth (12). Theplacement of bracket (26) in contact with “x” ridge portion (22) and “y”ridge portion (24) allows for the precise height, rotation andangulation placement of bracket (26) onto tooth (12) of model (10). Inother words, the alignment ridges (20) set the bracket fromfront-to-back and top-to-bottom of tooth (12). If, for example, bracket(26) is placed too far back on facial surface (16) of tooth (12),incorrect rotational movement may occur. After the placement of brackets(26) on teeth (12), adhesive (36) is then cured, preferably usingchemical or light activation.

Referring to FIG. 9, an indirect bonding tray or transfer tray (42) isformed over and in contact with brackets (26), and is used to transferbrackets (26) on model (10) to the patient's mouth. While an indirectbonding tray or transfer tray is disclosed herein to transfer thebrackets from the model to the patient's teeth, one skilled in the artwould understand that other systems or means could be used for transfer.Transfer tray (42) can also contain individual brackets for transfer.For purposes of this invention, transfer tray (42) should be semi-rigidand eventually allow the release of the orthodontic appliance.Preferably, transfer tray (42) is made with a silicone transfer materialmixed with an activating agent. Once the material and agent have beenmixed, the mixture is rolled into the shape of a cylinder and moldedover brackets (26). The occlusal and lingual surfaces of the teeth arepreferably covered with the tray mixture.

There are many ways to form transfer tray (42) and U.S. Pat. No.6,554,613, for example, gives a general discussion of a few such ways.It should be understood that the process by which transfer tray (42) isformed is not limited to the description in this application. Forexample, a Biostar unit can be used to form transfer tray (42). TheBiostar unit pressure forms a layer of soft material, over layered witha more rigid material. The layer of soft material is pressure formedonto model (10) first, and the excess material is trimmed off. The layerof more rigid material is then adapted and then trimmed away, since itis only to permit firm seating of the soft tray. The outer layerprovides rigidity to the transfer tray, and the inner layer permitseasier removal of the tray.

In addition, polyvinylsiloxane, or PVS, can be used to form transfertray (42). To form tray (42), two phases of PVS are used: a light bodymaterial and a heavy body material. The light body material is squirtedusing a syringe around set brackets (26) on model (10). The light bodymaterial flows into all the contours of brackets (26) and forms a gripon them. The heavy body material is then applied over the light bodymaterial to form a support tray.

To remove brackets (26) from model (10), model (10) with transfer tray(42) is preferably soaked in water for a sufficient time to permit theseparation of adhesive (36) from tooth (12). Referring to FIG. 10, astransfer tray (42) is removed from model (10), brackets (26) remainstuck to the inside of transfer tray (42) and pods (18) and ridges (20)on model (10) are left behind. FIG. 11 shows the inside of tray (42)with brackets (26) stuck and adhesive (36) exposed. Indentations (44)from pods (18) are shown in adhesive (36). A closer look at indentations(44) in FIG. 12 shows mesh base (34) at the bottom of indentations (44).Mesh base (34) can be seen as a result the contact between pods (18) andmesh base (34). Although pods (18) were in contact with mesh base (34),mesh base (34) may still have a very small layer of adhesive (36)covering it because of the surface area in the mesh.

The surface of adhesive (36) is then carefully cleaned usingmicro-etching or sandblasting. This ensures that a receptive surface ispresent in terms of receiving a clinical bonding agent. Any excessmaterial on tray (42) is also trimmed. After cleaning and trimming,conventional indirect bonding techniques are used to bond brackets (26)to the patient's teeth. A bonding agent is applied to brackets (26) andtransfer tray (42) is used to transport brackets (26) to the patient'steeth, as shown in FIG. 13. When transfer tray (42) is applied to thepatient's mouth, brackets (26) are removed from tray (42) in the properpositional relationship for application to the patient's teeth. In otherwords, brackets (26) are bonded to the patient's teeth in the sameoptimal position as they were placed on model (10) and adhesive (36)maintains the same spacing.

Other alternations and modifications of the invention will likewisebecome apparent to those of ordinary skill in the art upon reading thepresent disclosure, and it is intended that the scope of the inventiondisclosed herein be limited only by the broadest interpretation of theappended claims to which the inventor is legally entitled.

1. A method for indirectly positioning and bonding an orthodonticappliance on a maloccluded tooth, the method comprising the steps of:forming a physical model corresponding to teeth of a patient, the modelhaving a plurality of model teeth with each tooth having a facialsurface, and each maloccluded model tooth embodying at least oneprotuberance that is a unitary part of the facial surface and at leasttwo non-parallel cooperating ridges that are unitary parts of the facialsurface; obtaining at least one orthodontic appliance and applyingadhesive to a base of the at least one orthodontic appliance;positioning an orthodontic appliance over the at least one protuberanceand adjacent to the at least two ridges of a maloccluded model tooth;using the at least two ridges to guide the placement of the orthodonticappliance on the facial surface of a maloccluded model tooth; releasablymounting the at least one orthodontic appliance to the physical model ontop of the at least one protuberance and in contact with walls of the atleast two cooperating ridges; applying an adhesive to the base of anorthodontic appliance, wherein the adhesive is at least as thick as theheight of the at least one protuberance and at least at the position ofthe at least one protuberance on the facial surface; forming an adhesivelayer on the base of the at least one orthodontic appliance by allowingthe adhesive to spread and shape between the at least one tooth of themodel and the base; curing the adhesive layer; forming a transfer trayover the at least one tooth and the at least one orthodontic appliance;removing the transfer tray and the at least one orthodontic appliancefrom the model; and transferring and bonding the at least oneorthodontic appliance to the maloccluded teeth of the patient.
 2. Themethod of claim 1 further comprising the step of soaking the transfertray and model in a liquid to aid in releasing the adhesive from themodel.
 3. The method of claim 1 further comprising the step of cleaningthe adhesive after removal of the at least one orthodontic appliancefrom the model.
 4. The method of claim 1 wherein the physical model isformed by stereo lithography.
 5. The method of claim 1 wherein thephysical model is formed by molding.
 6. The method of claim 1 whereinthe physical model is formed by carving.
 7. The method of claim 1wherein the model is formed from a polymeric material.
 8. The method ofclaim 1 wherein the at least one protuberance has a maximum height ofabout half a millimeter.
 9. The method of claim 1 wherein eachmaloccluded model tooth embodies from one to four protuberances.
 10. Themethod of claim 1 wherein at least one maloccluded model tooth embodiesat least two protuberances of different heights.
 11. The method of claim1 wherein at least one maloccluded model tooth embodies twoprotuberances that are unitary parts of the facial surface.
 12. Themethod of claim 1 wherein at least one maloccluded model tooth embodiesthree protuberances that are unitary parts of the facial surface. 13.The method of claim 1 wherein at least one maloccluded model toothembodies four protuberances that are unitary parts of the facialsurface.
 14. The method of claim 1 wherein a plurality of orthodonticappliances are transferred and bonded to a patient's maloccluded teeth.15. A method of forming a physical model to aid in positioningorthodontic appliances on a patient's teeth according to a positionobtained from a virtual model, the method comprising the steps of:creating a virtual original malocclusion model of a patient's teeth,including the facial surfaces thereof; manipulating the virtual originalmalocclusion model to simulate movement of individual teeth to acorrected position; creating a virtual corrected malocclusion model fromthe manipulated virtual original malocclusion model based on the finalcorrected teeth positions; positioning a virtual orthodontic applianceon the virtual original malocclusion model according to the correctedpositions obtained from the virtual corrected malocclusion model;modifying at least one virtual original malocclusion model tooth toembody at least one virtual protuberance that is a unitary part of thefacial surface where the size, position, and orientation of the at leastone virtual protuberance correspond to the spacing, positioning, andorientation of the virtual orthodontic appliance on the virtual originalmalocclusion model; modifying at least one virtual original malocclusionmodel tooth to embody at least two non-parallel cooperating virtualridges that are unitary parts of the facial surface, where the size,position, and orientation of the at least two cooperating virtual ridgescorrespond to the spacing, positioning, and orientation of the virtualorthodontic appliance on the virtual original malocclusion model; andforming a physical model of the modified virtual original malocclusionmodel with at least one physical maloccluded model tooth embodying atleast one protuberance and at least two cooperating non-parallel ridgesthat are unitary parts of the facial surface, wherein the size,position, and orientation of the at least one protuberance and the atleast two ridges embodied on the physical model tooth correspond to thesize, position, and orientation of the at least one virtual protuberanceand the at least two cooperating virtual ridges on the facial surface ofthe at least one modified virtual original malocclusion model tooth.